CN111682777A - Secondary parallel LCD forward converter capable of avoiding reverse charging of energy storage capacitor - Google Patents

Secondary parallel LCD forward converter capable of avoiding reverse charging of energy storage capacitor Download PDF

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CN111682777A
CN111682777A CN202010490672.0A CN202010490672A CN111682777A CN 111682777 A CN111682777 A CN 111682777A CN 202010490672 A CN202010490672 A CN 202010490672A CN 111682777 A CN111682777 A CN 111682777A
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diode
forward converter
capacitor
inductor
max
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CN111682777B (en
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刘树林
杨莹
李思远
张元昌
王航杰
严纪志
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Xian University of Science and Technology
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Xian University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0051—Diode reverse recovery losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a secondary side parallel LCD forward converter capable of avoiding reverse charging of an energy storage capacitor, which comprises a forward converter main circuit and an energy transfer and transmission circuit, wherein the forward converter main circuit comprises a high-frequency transformer T, a switching tube S, a diode D1, a diode D2, an inductor L1 and a capacitor C1, and the energy transfer and transmission circuit comprises a diode D3, a capacitor C2, an inductor L2 and a diode D4. The circuit has simple structure and high reliability, the diode D4 ensures that the C2 can not be charged reversely, the reactive loss of the converter is reduced, the reverse recovery problem of D4 can be eliminated, the loss of the diode is reduced, the excitation energy is transferred to the load side, the forward energy can be transmitted, the energy transmission efficiency is improved, and the high-power transmission circuit is suitable for high-power transmission.

Description

Secondary parallel LCD forward converter capable of avoiding reverse charging of energy storage capacitor
Technical Field
The invention belongs to the technical field of switching power supplies, and particularly relates to a secondary side parallel LCD forward converter capable of avoiding reverse charging of an energy storage capacitor.
Background
In many isolated switching power supply conversion topologies, compared with a flyback converter, the power of a forward converter is not limited by the energy storage capacity of a transformer; compared with half-bridge converters and full-bridge converters, forward converters have fewer used components, simpler circuits, lower cost and higher reliability. Therefore, the forward converter circuit is more suitable for being applied to medium and small power electric energy conversion occasions due to the advantages of relatively simple structure, low cost, input and output isolation, high working reliability and the like, and is highly concerned by the industry.
However, in the case of the single-tube forward converter, because the high-frequency transformer core is magnetized unidirectionally when the single-tube forward converter operates in a forward excitation state, the high-frequency transformer core does not have a magnetic reset function, and thus the single-tube forward converter has a high possibility of causing problems such as magnetic core saturation and the like. The current flowing through the switching tube is increased suddenly as a result of magnetic saturation, and even the switching tube is damaged, so that the popularization of the forward converter is limited to a great extent, and a special magnetic reset circuit or an energy transfer circuit must be added to avoid magnetic core saturation.
The main operating mechanism of the magnetic reset circuit is to transfer the excitation energy in the off time of the switch in each period, and the excitation energy can be consumed on other devices or returned to the input power supply or transmitted to the load side. The magnetic reset circuits adopted by the existing forward converter are various, and are roughly divided into three types:
firstly, a reset winding is connected to an input end to return energy to an input power supply;
secondly, a primary side of the transformer is connected with reset circuits such as an RCD (resistor capacitor diode), an LCD (liquid crystal display) and the like, so that energy is consumed or returns to an input end;
thirdly, a reset measure is taken on the secondary side, and energy can be transferred to the output end.
However, the conventional RCD clamp circuit is relatively simple, and has the disadvantage that excitation energy is consumed in the clamp resistor, so that the overall efficiency of the system is difficult to improve; the magnetic reset can be realized by adopting an active clamping technology, which is a method with excellent performance, but increases the complexity, the design difficulty and the cost of a converter circuit; the magnetic reset winding reset method is mature and reliable in technology, excitation energy can be returned to an input power supply, but the magnetic reset winding increases the complexity of the transformer structure and increases the voltage stress of the power switch tube.
The existing secondary side reset either needs to increase a reset winding or makes a circuit complex, but increases the design and manufacturing difficulty and cost of a transformer or the circuit; or more diodes are needed to realize energy transfer, but the circuit loss is increased; or the operating mode or other electrical performance indexes of the forward inductor can be influenced, which is not beneficial to high-power transmission.
Therefore, in order to further popularize and apply the forward converter, solve the problem of magnetic reset, improve the comprehensive performance of the forward converter, and solve the defects of other reset modes, research on a new magnetic reset mode is a problem which needs to be continuously studied.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art, provides a secondary side parallel connection LCD forward converter capable of avoiding reverse charging of an energy storage capacitor, and solves the problems of low excitation energy utilization rate, complex circuit composition, high loss, low efficiency and the like of the existing magnetic reset circuit.
In order to solve the technical problems, the invention adopts the technical scheme that: the utility model provides a can avoid parallelly connected LCD forward converter of vice limit of energy storage capacitor reverse charging which characterized in that: the energy transfer and transmission circuit comprises a forward converter main circuit (1) and an energy transfer and transmission circuit (2) connected with the forward converter main circuit (1); the forward converter main circuit (1) comprises a high-frequency transformer T, a switching tube S, a diode D1, a diode D2, an inductor L1 and a capacitor C1, wherein the dotted end of the primary side of the high-frequency transformer T is the positive voltage input end IN + of the forward converter main circuit (1) and is connected with the positive output end of an external power supply, the dotted end of the primary side of the high-frequency transformer T is connected with the drain electrode of the switching tube S, the source electrode of the switching tube S is the negative voltage input end IN-of the forward converter main circuit (1) and is connected with the negative output end of the external power supply, the grid electrode of the switching tube S is connected with the output end of an external controller, the dotted end of the secondary side of the high-frequency transformer T is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the cathode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is connected with one end of the capacitor C1 and is the positive voltage output, the synonym end of the secondary side of the high-frequency transformer T is connected with the anode of the diode D2 and the other end of the capacitor C1 and is the negative voltage output end OUT-of the forward converter main circuit (1), and the negative voltage output end OUT-of the forward converter main circuit (1) is grounded; the energy transfer and transmission circuit (2) comprises a diode D3 and a capacitor C2, wherein the anode of the diode D3 is connected with the anode of a diode D2, the cathode of the diode D3 is connected with the second end of a capacitor C2, and the first end of the capacitor C2 is connected with the anode of a diode D1; the energy transfer and transmission circuit (2) comprises a diode D3, a capacitor C2, an inductor L2 and a diode D4, wherein the anode of the diode D3 is connected with the anode of a diode D2, the cathode of the diode D3 is connected with the second end of the capacitor C2, the first end of the capacitor C2 is connected with the anode of a diode D1, one end of the inductor L2 is connected with the cathode of a diode D3, the other end of the inductor L2 is connected with the positive voltage output end OUT + of the forward converter main circuit (1), the anode of the diode D4 is connected with the first end of a capacitor C2 of the energy transfer and transmission circuit (2), and the second end of a cathode capacitor C2 of the diode D4 is connected.
Wherein, the preferred scheme is: the diodes D1, D2 are fast recovery diodes.
Wherein, the preferred scheme is: the switch tube S is a full-control power semiconductor device.
Wherein, the preferred scheme is: the capacitor C2 is selected according to a first selection step; wherein the step of the first selecting step comprises:
step 101, selecting a capacitance value C of an excitation energy storage capacitor C22,；
Step 102, calculating the voltage withstanding value V of the capacitor C2C2,Ton；
Step 103, selecting the capacity value C2And the withstand voltage value is larger than VC2,TonAs the capacitance C2.
Wherein, the preferred scheme is: the inductor L2 is selected according to a second selection step; wherein the second selecting step comprises the following steps:
step 201, obtaining an average value of current variation flowing through an inductor L2 in the whole period, and obtaining an average current of an inductor L1;
step 202, determining the inductance L of the inductor L22The value range of (a);
step 203, combining step 201 and step 202, determines the maximum current I flowing through the inductor L2L2,max。
Wherein, the preferred scheme is: the diode D3 and the diode D4 are selected according to a third selection step; wherein the third selecting step comprises the following steps:
step 301, calculating the maximum current I flowing through the diode D3D3,max；
Step 302, calculating the maximum withstand voltage V of the diode D3D3,max；
Step 303, according to the maximum current I flowing through the diode D3D3,maxAnd a withstand voltage value V of the diode D3D3,maxA selection diode D3;
step 304, calculating the maximum current I flowing through the diode D4D4,max；
Step 305, calculating the maximum voltage withstanding value V of the diode D4D4,max；
Step 306, according to the maximum current I flowing through the diode D4D4,maxAnd a withstand voltage value V of the diode D4D4,maxDiode D4 is selected.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the secondary side capable of preventing the energy storage capacitor from being reversely charged is connected with the LCD forward converter in parallel, so that the excitation energy is transferred to the load side, and the overall efficiency of the converter is improved.
2. The secondary side parallel LCD forward converter designed and realized by the invention has high working stability and reliability, simple circuit, no need of complex control scheme and wider popularization value.
3. The secondary side LCD magnetic reset forward converter circuit designed by the invention resets relative to the auxiliary winding, thereby reducing the design difficulty of the transformer.
4. The capacitor of the energy transfer and transmission circuit is connected with the unidirectional conductive diode in parallel, so that the reverse charging of C2 can be prevented, the reactive power is reduced, and the efficiency is further improved.
5. The reverse recovery problem of the diode D4 can be eliminated, and the diode loss is reduced.
6. Inductor L2 may operate in CCM, suitable for high power transmission.
7. The energy transfer and transmission circuit can also transmit forward energy, can disperse power transmission, further improves the reliability, and is more suitable for high-power application.
8. After the switching power supply is used, the switching power supply has higher working safety and reliability, the energy transfer and transmission circuit can improve the energy utilization rate, and the switching power supply can be widely applied to the fields of computers, medical communication, industrial control, aerospace equipment and the like, so the switching power supply has higher popularization and application values;
in summary, the circuit of the invention has the advantages of simple structure, convenient implementation, low cost, simple working mode, high working stability and reliability, long service life, low power consumption, high utilization rate of the transformer, high energy transmission efficiency, capability of improving the working safety and reliability of the switching power supply, strong practicability and high popularization and application value.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic circuit diagram of a secondary side parallel LCD forward converter capable of avoiding reverse charging of an energy storage capacitor according to the present invention.
Description of reference numerals:
1-forward converter main circuit; 2-energy transfer and transmission circuit.
Detailed Description
As shown in fig. 1, the secondary side parallel LCD forward converter capable of preventing the energy storage capacitor from being reversely charged according to the present invention includes a forward converter main circuit 1, and an energy transfer and transmission circuit 2 connected to the forward converter main circuit 1; the forward converter main circuit 1 comprises a high-frequency transformer T, a switching tube S, a diode D1, a diode D2, an inductor L1 and a capacitor C1, wherein the dotted terminal of the primary side of the high-frequency transformer T is the positive voltage input terminal IN + of the forward converter main circuit 1 and is connected with the positive output terminal of an external power supply, the dotted terminal of the primary side of the high-frequency transformer T is connected with the drain electrode of the switching tube S, the source electrode of the switching tube S is the negative voltage input terminal IN-of the forward converter main circuit 1 and is connected with the negative output terminal of the external power supply, the grid electrode of the switching tube S is connected with the output terminal of an external controller, the dotted terminal of the secondary side of the high-frequency transformer T is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the cathode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is connected with one end of the capacitor C1 and is the positive, the synonym end of the secondary side of the high-frequency transformer T is connected with the anode of the diode D2 and the other end of the capacitor C1 and is the negative voltage output end OUT-of the forward converter main circuit 1, and the negative voltage output end OUT-of the forward converter main circuit 1 is grounded; the energy transfer and transmission circuit 2 comprises a diode D3 and a capacitor C2, wherein the anode of the diode D3 is connected with the anode of a diode D2, the cathode of the diode D3 is connected with the second end of a capacitor C2, and the first end of the capacitor C2 is connected with the anode of a diode D1; the energy transfer and transmission circuit 2 comprises a diode D3, a capacitor C2, an inductor L2 and a diode D4, wherein the anode of the diode D3 is connected with the anode of a diode D2, the cathode of the diode D3 is connected with the second end of the capacitor C2, the first end of the capacitor C2 is connected with the anode of a diode D1, one end of the inductor L2 is connected with the cathode of a diode D3, the other end of the inductor L2 is connected with the positive voltage output end OUT + of the forward converter main circuit 1, the anode of the diode D4 is connected with the first end of the capacitor C2 of the energy transfer and transmission circuit 2, and the second end of the cathode capacitor C2 of the diode D4 is connected.
In specific implementation, the load RL is connected between the positive voltage output end OUT + and the negative voltage output end OUT-of the forward converter main circuit 1. In the forward converter main circuit 1, an inductor L1 and a capacitor C1 are used for filtering.
In this embodiment, the diode D1 is a rectifying diode, and the diode D2 is a fast recovery diode. Diode D2 is used for freewheeling.
In this embodiment, the switch tube S is an NMOS switch tube.
The working principle of the embodiment is as follows:
before analyzing the operation principle of the present embodiment, it is assumed that the forward inductor L1 operates in DCM, and the auxiliary inductor L2 and the transformer secondary inductor Lw2 operate in CCM. The operation principle of the present embodiment is analyzed below by dividing the off period and the on period of the switching tube. For ease of introducing the principle, convention: for C2, assume that its voltage is positive left negative right, and positive left negative reverse.
Firstly, the working principle of the switching tube S during conduction:
assuming that the forward voltage of C2 is at a maximum value before the switch turn-on time, the Lw2 and L2 currents drop to a minimum value, and the inductor L1 current remains at zero. D3 is turned on, and D1, D2 and D4 are turned off.
The first stage is as follows: d4 is turned off, and C2 releases positive stored energy
After the switching tube is conducted, the input voltage Vi is applied to two ends of a primary winding of the transformer, the voltage coupled to the secondary winding w2 is positive, negative and positive, the D1 is conducted, the forward excitation energy is transmitted to the load through the two branches, one of the forward excitation energy is transmitted to the load through the D1 and the L1, and the L1 current rises linearly. Secondly, energy is transferred to the load through C2, D4 and L2, the C2 positive stored energy is released from the maximum value, the L2 current curve rises until the C2 positive voltage drops to zero, and the stage is finished. At this stage, D2, D3, D4 remained off.
And a second stage: d4 is turned on to transfer energy to load via D4 and L2
When the forward voltage of the C2 drops to zero, the D4 is naturally conducted, the C2 is short-circuited, energy is transmitted to the load through the D4 and the L2, and the L2 current keeps rising linearly. Meanwhile, D1 is still kept on, the current L1 continues to rise linearly until the next switch off period comes, the currents L1 and L2 reach the maximum values, and the process is finished. At this stage, D4 zero voltage conduction is achieved.
Secondly, the working principle of the switching tube S during the turn-off period is as follows:
the first stage is as follows: l1, L2 simultaneously providing energy to the load
After the switch tube S is turned off, the D3 is conducted, the secondary winding stores energy to the C2 in the positive direction through the D3, and the voltage at the two ends of the C2 starts to increase in the positive direction from zero. At the same time, inductor L2 freewheels through D3, and inductor L2 current drops linearly. In the process, D2 is turned on, L1 continues to supply energy to the load through D2, the current of the inductor L1 linearly decreases until the current of L1 decreases to zero, and the stage ends.
And a second stage: only the L2 freewheel provides energy to the load
After the current of the inductor L1 drops to zero, the D2 is cut off, the D3 is kept on, the C2 continues to store excitation energy, the forward voltage of the C2 gradually increases, and the current coupled to the secondary winding slowly drops. At the same time, inductor L2 continues freewheeling via D3. Until the next switch on period, the L2 current and the current coupled to the secondary winding both drop to a minimum, the C2 voltage reaches a maximum, and this phase ends.
In this embodiment, the capacitor C2 is selected according to a first selection step; wherein the step of the first selecting step comprises:
step 101, according to a formula
Figure BDA0002520958090000071
Selecting the capacitance value C of an excitation energy storage capacitor C22；
102, calculating the withstand voltage value V of the capacitor C2 according to the formula (A1)C2,Ton；
Figure BDA0002520958090000081
Wherein d is the duty ratio of the switching tube S, n is the turn ratio of the primary winding and the secondary winding of the high-frequency transformer T, and LmThe exciting inductance of the primary winding of the high-frequency transformer T, f is the working frequency of the main circuit 1 of the forward converter, lambda is generally equal to or more than 0.8 and equal to or less than 1, and the exciting inductance LmThe maximum exciting current in one period is ILm,maxWith a minimum excitation current of ILm,minThe concrete formula is:
Figure BDA0002520958090000082
wherein, ViInputting voltage for a main circuit 1 of the forward converter;
step 103, selecting the capacity value C2And the withstand voltage value is larger than VC2,TonAs the capacitance C2.
In this embodiment, the inductor L2 is selected according to a second selection step; wherein the second selecting step comprises the following steps:
step 201, determining the inductance value L of the inductor L2 according to the formula (A8) and the formula (A9)2The value range of (a);
Figure BDA0002520958090000083
Figure BDA0002520958090000084
wherein, VoIs the output voltage of the main circuit 1 of the forward converter;
step 202, determining the maximum current I flowing through the inductor L2 according to the formula (A10)L2,max；
Figure BDA0002520958090000091
Wherein, the time for the voltage across the capacitor C2 to drop to zero is
Figure BDA0002520958090000092
Before the voltage across the capacitor C2 of the inductor L2 does not drop to zero, the current expression of the inductor L2 is
Figure BDA0002520958090000093
The average value of the variation of the current flowing through the inductor L2 in the whole period is
Figure BDA0002520958090000094
The average current of the inductor L1 is
Figure BDA0002520958090000095
In this embodiment, the diodes D3 and D4 are selected according to a third selection step; wherein the second selecting step comprises the following steps:
step 301, calculating the maximum current I flowing through the diode D3 according to the formula (A15)D3,max
Figure BDA0002520958090000096
Wherein, IL1,maxFor the maximum current flowing through the primary winding of the high-frequency transformer T, IL2Is the current through inductor L2;
step 302, calculating the maximum withstand voltage V of the diode D3 according to the formula (A16)D3,max
Figure BDA0002520958090000097
Step 303, according to the maximum current I flowing through the diode D3D3,maxAnd a withstand voltage value V of the diode D3D3,maxDiode D3 is selected.
Step 304, calculating the maximum current I flowing through the diode D4 according to the formula (A17)D4,max；
Figure BDA0002520958090000101
Step 305, calculating the maximum voltage withstanding value V of the diode D4 according to the formula (A18)D4,max；
Figure BDA0002520958090000102
Step 303, according to the maximum current I flowing through the diode D4D4,maxAnd withstand voltage of diode D4Value VD4,maxDiode D4 is selected.
Of course, the above description is only for illustrating the feasibility of the technical solution of the present invention, and the principle of one of the operation modes and the corresponding formula are listed, but not the only and limited description, which is used as reference.
It should be particularly noted that the above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and it is obvious for those skilled in the art to modify the technical solutions described in the above-mentioned embodiments or to substitute part of the technical features thereof; and all such modifications and alterations are intended to fall within the scope of the appended claims.

Claims (6)

1. The utility model provides a can avoid parallelly connected LCD forward converter of vice limit of energy storage capacitor reverse charging which characterized in that: the energy transfer and transmission circuit comprises a forward converter main circuit (1) and an energy transfer and transmission circuit (2) connected with the forward converter main circuit (1); the forward converter main circuit (1) comprises a high-frequency transformer T, a switching tube S, a diode D1, a diode D2, an inductor L1 and a capacitor C1, wherein the dotted end of the primary side of the high-frequency transformer T is the positive voltage input end IN + of the forward converter main circuit (1) and is connected with the positive output end of an external power supply, the dotted end of the primary side of the high-frequency transformer T is connected with the drain electrode of the switching tube S, the source electrode of the switching tube S is the negative voltage input end IN-of the forward converter main circuit (1) and is connected with the negative output end of the external power supply, the grid electrode of the switching tube S is connected with the output end of an external controller, the dotted end of the secondary side of the high-frequency transformer T is connected with the anode of the diode D1, the cathode of the diode D1 is connected with the cathode of the diode D2 and one end of the inductor L1, the other end of the inductor L1 is connected with one end of the capacitor C1 and is the positive voltage output, the synonym end of the secondary side of the high-frequency transformer T is connected with the anode of the diode D2 and the other end of the capacitor C1 and is the negative voltage output end OUT-of the forward converter main circuit (1), and the negative voltage output end OUT-of the forward converter main circuit (1) is grounded; the energy transfer and transmission circuit (2) comprises a diode D3, a capacitor C2, an inductor L2 and a diode D4, wherein the anode of the diode D3 is connected with the anode of a diode D2, the cathode of the diode D3 is connected with the second end of the capacitor C2, the first end of the capacitor C2 is connected with the anode of a diode D1, one end of the inductor L2 is connected with the cathode of a diode D3, the other end of the inductor L2 is connected with the positive voltage output end OUT + of the forward converter main circuit (1), the anode of the diode D4 is connected with the first end of a capacitor C2 of the energy transfer and transmission circuit (2), and the second end of a cathode capacitor C2 of the diode D4 is connected.
2. The secondary side parallel LCD forward converter capable of avoiding reverse charging of the energy storage capacitor as claimed in claim 1, wherein: the diodes D1, D2 are fast recovery diodes.
3. The secondary side parallel LCD forward converter capable of avoiding reverse charging of the energy storage capacitor as claimed in claim 1, wherein: and the switching tube S is a fully-controlled power semiconductor device.
4. The secondary side parallel LCD forward converter capable of avoiding reverse charging of the energy storage capacitor as claimed in claim 1, wherein: the capacitor C2 is selected according to a first selection step; wherein the step of the first selecting step comprises:
step 101, selecting a capacitance value C of an excitation energy storage capacitor C22,；
Step 102, calculating the voltage withstanding value V of the capacitor C2C2,Ton；
Step 103, selecting the capacity value C2And the withstand voltage value is larger than VC2,TonAs the capacitance C2.
5. The secondary side parallel LCD forward converter capable of avoiding reverse charging of the energy storage capacitor as claimed in claim 4, wherein: the inductor L2 is selected according to a second selection step; wherein the second selecting step comprises the following steps:
step 201, obtaining an average value of current variation flowing through an inductor L2 in the whole period, and obtaining an average current of an inductor L1;
step 202, determining the inductance L of the inductor L22The value range of (a);
step 203, combining step 201 and step 202, determines the maximum current I flowing through the inductor L2L2,max。
6. The secondary side parallel LCD forward converter capable of avoiding the reverse charging of the energy storage capacitor as claimed in claim 4 or 5, wherein: the diode D3 and the diode D4 are selected according to a third selection step; wherein the third selecting step comprises the following steps:
step 301, calculating the maximum current I flowing through the diode D3D3,max；
Step 302, calculating the maximum withstand voltage V of the diode D3D3,max；
Step 303, according to the maximum current I flowing through the diode D3D3,maxAnd a withstand voltage value V of the diode D3D3,maxA selection diode D3;
step 304, calculating the maximum current I flowing through the diode D4D4,max；
Step 305, calculating the maximum voltage withstanding value V of the diode D4D4,max；
Step 306, according to the maximum current I flowing through the diode D4D4,maxAnd a withstand voltage value V of the diode D4D4,maxDiode D4 is selected.
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